There's a tendency to describe any enclosed and dangerous space visited by heroes as a "dungeon". After all, the game's called Dungeons & Dragons. Literally, though, a dungeon is really only something found beneath a fortification or palace, used for the the primary or ancillary purpose of detaining prisoners.
Keep on the Shadowfell promises a ruined keep as its main location. As players set out from Winterhaven for their first journey to this key structure, they may be looking forward to standing at ancient battlements, crossing haunted courtyards, peering through weathered murder holes, and nervously exploring crumbling feast-halls.
Upon arriving, they find that the keep's been reduced almost totally to rubble, there is clearly nothing of interest at surface level, and in the middle of the ruins is a recently-used and well-maintained stairway leading down to the crypts. There may as well be a large arrow pointing downwards, helpfully labelled "Dungeon!".
Keep on the Shadowfell has already laid down its credentials as an unapologetically old-school dungeon crawler, so in a way it's refreshing that it gets right down to business like this. It's still a little jarring though. The internet reveals my players weren't alone in finding it hard to believe that the entire setup of the "keep" was just window-dressing on a series of crypts.
Probably a more accurate name would have been "Crypt On The Shadowfell".